Systems and Methods for Modifying LIDAR Field of View

ABSTRACT

The present disclosure relates to systems, methods, and vehicles that facilitate a light detection and ranging (LIDAR or lidar) system that may take advantage of “dead angles” where the lidar system is oriented toward support structure or another “uninteresting” feature. In such scenarios, light pulses may be redirected toward more-interesting features in the environment. An example system includes a lidar system configured to emit light pulses into an environment of the system so as to provide information indicative of objects within a default field of view. The system also includes a reflective surface optically coupled to the lidar system. The reflective surface is configured to reflect at least a portion of the emitted light pulses so as to provide an extended field of view. The lidar system is further configured to provide information indicative of objects within the extended field of view.

BACKGROUND

A conventional Light Detection and Ranging (LIDAR or lidar) system mayutilize a light-emitting transmitter (e.g., a laser diode) to emit lightpulses into an environment. Emitted light pulses that interact with(e.g., reflect from) objects in the environment can be received by areceiver (e.g., a photodetector) of the LIDAR system. Range informationabout the objects in the environment can be determined based on a timedifference between an initial time when a light pulse is emitted and asubsequent time when the reflected light pulse is received.

SUMMARY

The present disclosure generally relates to light detection and ranging(LIDAR or lidar) systems, which may be configured to obtain informationabout an environment. Such lidar devices may be implemented in vehicles,such as autonomous and semi-autonomous automobiles, trucks, motorcycles,and other types of vehicles that can move within their respectiveenvironments.

In a first aspect, a system is provided. The system includes a lidarsystem configured to emit light pulses into an environment of the systemso as to provide information indicative of objects within a defaultfield of view. The lidar system includes a rotatable base configured torotate about a first axis and a rotatable mirror coupled to therotatable base. The rotatable mirror is configured to rotate about asecond axis. The lidar system also includes at least one light sourceconfigured to emit the light pulses. The emitted light pulses interactwith the environment to provide return light pulses. The lidar systemadditionally includes at least one detector configured to detect atleast a portion of the return light pulses. The system also includes areflective surface optically coupled to the lidar system. The reflectivesurface is configured to reflect at least a portion of the emitted lightpulses so as to provide an extended field of view. The lidar system isfurther configured to provide information indicative of objects withinthe extended field of view.

In a second aspect, a method is provided. The method includes causing atleast one light source of a lidar system to emit light pulses toward adefault field of view and toward a reflective surface configured toreflect a portion of the light pulses toward an extended field of view.The lidar system includes a rotatable base configured to rotate about afirst axis and a rotatable mirror coupled to the rotatable base. Therotatable mirror is configured to rotate about a second axis. The lidarsystem also includes at least one light source configured to emit thelight pulses. The emitted light pulses interact with the environment toprovide return light pulses. The lidar system additionally includes atleast one detector configured to detect at least a portion of the returnlight pulses. The emitted light pulses interact with an environment ofthe lidar system to provide return light pulses. The method alsoincludes receiving at least a first portion of the return light pulsesfrom the default field of view as a first detected light signal. Themethod additionally includes receiving at least a second portion of thereturn light pulses from the extended field of view as a second detectedlight signal. Yet further, the method includes transmitting point clouddata, wherein the point cloud data is based on the first detected lightsignal and the second detected light signal, and indicative of objectswithin the default field of view and the extended field of view.

In a third aspect, a vehicle is provided. The vehicle includes a lidarsystem configured to emit light pulses into an environment of thevehicle so as to provide information indicative of objects within adefault field of view. The lidar system includes a rotatable baseconfigured to rotate about a first axis and a rotatable mirror coupledto the rotatable base. The rotatable mirror is configured to rotateabout a second axis. The lidar system also includes at least one lightsource configured to emit the light pulses. The emitted light pulsesinteract with the environment to provide return light pulses. The lidarsystem additionally includes at least one detector configured to detectat least a portion of the return light pulses. The vehicle additionallyincludes a reflective surface optically coupled to the lidar system. Thereflective surface is configured to reflect at least a portion of theemitted light pulses so as to provide an extended field of view. Thelidar system is further configured to provide information indicative ofobjects within the extended field of view.

Other aspects, embodiments, and implementations will become apparent tothose of ordinary skill in the art by reading the following detaileddescription, with reference where appropriate to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates a system, according to an example embodiment.

FIG. 2A illustrates a lidar system, according to an example embodiment.

FIG. 2B illustrates a lidar system, according to an example embodiment.

FIG. 2C illustrates a portion of the lidar system of FIG. 2A, accordingto an example embodiment.

FIG. 2D illustrates a lidar system, according to an example embodiment.

FIG. 3 illustrates a system, according to an example embodiment.

FIG. 4 illustrates a system, according to an example embodiment.

FIG. 5A illustrates a vehicle, according to an example embodiment.

FIG. 5B illustrates a vehicle, according to an example embodiment.

FIG. 5C illustrates a vehicle, according to an example embodiment.

FIG. 5D illustrates a vehicle, according to an example embodiment.

FIG. 5E illustrates a vehicle, according to an example embodiment.

FIG. 6 illustrates an operating scenario, according to an exampleembodiment.

FIG. 7 illustrates a method, according to an example embodiment.

DETAILED DESCRIPTION

Example methods, devices, and systems are described herein. It should beunderstood that the words “example” and “exemplary” are used herein tomean “serving as an example, instance, or illustration.” Any embodimentor feature described herein as being an “example” or “exemplary” is notnecessarily to be construed as preferred or advantageous over otherembodiments or features. Other embodiments can be utilized, and otherchanges can be made, without departing from the scope of the subjectmatter presented herein.

Thus, the example embodiments described herein are not meant to belimiting. Aspects of the present disclosure, as generally describedherein, and illustrated in the figures, can be arranged, substituted,combined, separated, and designed in a wide variety of differentconfigurations, all of which are contemplated herein.

Further, unless context suggests otherwise, the features illustrated ineach of the figures may be used in combination with one another. Thus,the figures should be generally viewed as component aspects of one ormore overall embodiments, with the understanding that not allillustrated features are necessary for each embodiment.

I. Overview

Autonomous and semi-autonomous vehicles may utilize a three-dimensional(3D) lidar system for navigation by mapping out an environment of thevehicle based on a lidar point map. However, conventional lidars have“blind spots”, such as a limited range of elevations it can see down to,potentially leaving a cone or other region below the lidar, which is notscanned.

An example lidar system includes a rotatable mirror assembly and anoptical cavity. The optical cavity includes at least one light-emitterdevice, at least one photodetector, and respective optical elements(e.g., lenses). The light-emitter device may emit light pulses along alight-emission axis that interact with the rotatable mirror assembly sothat the light pulses are redirected into an environment. Light pulsesthat reflect back toward the lidar from the environment can be receivedby the photodetector along a light-receiving axis so as to determine adistance to target (range) and be used to form a point cloudrepresenting the distance determinations. In some embodiments, the lightpulses could be emitted through two windows located at opposing sides ofthe lidar system housing. While some embodiments may describe sensingdevices that utilize light pulses, it will be understood that othertypes of three-dimensional sensing technologies that utilize continuouswave light (e.g., continuous wave time-of-flight (TOF)) systems arepossible and contemplated.

In an example embodiment, the optical cavity could be coupled to arotatable base, which is configured to rotate about a first axis ofrotation that is substantially vertical. The mirror assembly could beconfigured to rotate about a second axis of rotation that is coincidentand substantially perpendicular to the first axis of rotation.

In such lidar systems, segments of a lidar point cloud can fall upon asupport structure (e.g., a structure that supports the lidar system on avehicle) or other features not of interest for the application to whichthe lidar is being applied. For example, in some scenarios, some lightpulses may be directed toward static (e.g., unchanging) or previouslycharacterized portions of the environment of the lidar. As describedherein, it is possible to recover useful point cloud information fromthese “uninteresting” light pulses by redirecting them with a reflectivesurface or mirror toward a different portion of the environment. Asdescribed herein the term “point cloud” could include a visualization ofrange information provided by the lidar and/or the raw range dataitself. It will be understood that, in some embodiments, such range dataneed not be stored on the lidar device itself and such visualizationsneed not be provided by the lidar device itself.

Systems and methods described herein may take advantage of “dead angles”where the scanner is looking at a vehicle structure or a supportstructure. In such scenarios, light pulses may be redirected towardinteresting features in the environment.

The lidar system disclosed herein could be used in or with machinevision and/or perception applications. In some embodiments, the lidarsystem could be utilized for transportation applications (e.g., semi- orfully-autonomous vehicles) or robotic, security, surveying,agricultural, mining, construction, marine, UAV, and/orwarehouse-related applications.

II. Example Systems

FIG. 1 illustrates a system 100, according to an example embodiment. Thesystem 100 includes a lidar system 200, which is configured to emitlight pulses into an environment of the system so as to provideinformation indicative of objects within a default field of view 102.The system 100 also includes a reflective surface 180 optically coupledto the lidar system 200. The reflective surface 180 is configured toreflect at least a portion of the emitted light pulses so as to providean extended field of view 182. The lidar system 200 is furtherconfigured to provide information indicative of objects within theextended field of view 182.

While lidar system 200 is described herein as being a laser-basedranging system, it will be understood that other types ofthree-dimensional sensors could be utilized in system 100. For example,system 100 could be utilized with another type of laser time-of-flightsystem, stereo cameras, or a camera with texture projectors.

In some example embodiments, lidar system 200 could include a rotatablebase 110 configured to rotate about a first axis. The rotatable base 110could include, or could be coupled to, a base actuator 112. In someembodiments, the base actuator 112 could be a brushless motor, a directcurrent (DC) motor, or another type of rotational actuator. In someexamples, the rotatable base 110 could be configured to rotate about thefirst axis at between 200 revolutions per minute (RPM) and 800 RPM. Itwill be understood that the rotatable base 110 could operate at otherrotational speeds. In some embodiments, the base actuator 112 could becontrolled by the controller 150 to rotate at a desired rotationalspeed. In some embodiments, lidar system 200 need not include arotatable base. In such scenarios, one or more elements of the lidarsystem 200 may be arranged with respect to the first axis. However, insuch cases, elements of the lidar system 200 need not rotate about thefirst axis. Accordingly, in such embodiments, lidar system 200 could beutilized in line-scanning applications, among other possibilities.

lidar system 200 also includes a mirror assembly 130. The mirrorassembly 130 is configured to rotate about a second axis. In suchscenarios, the second axis could be substantially perpendicular to thefirst axis (e.g., within 0 to 10 degrees of perpendicular). In someembodiments, the mirror assembly 130 includes a plurality of reflectivesurfaces 132. Additionally, the mirror assembly 130 could include ashaft 134 and a multi-sided mirror that is configured to mount theplurality of reflective surfaces 132. The mirror assembly 130 could alsoinclude a mirror actuator 136, which could be a brushless motor, a DCmotor, or another type of rotational actuator. In such scenarios, themirror actuator 136 is coupled to the shaft 134. In some embodiments,the mirror actuator 136 could be configured to rotate the multi-sidedmirror about the second axis at a rotational speed between 20,000 RPMand 40,000 RPM. It will be understood that the mirror actuator 136 couldbe operated at various rotational speeds or a desired rotational speed,which could be controlled by the controller 150.

In such scenarios, the plurality of reflective surfaces 132 couldinclude three reflective surfaces arranged symmetrically about thesecond axis such that at least a portion of the mirror assembly 130 hasa triangular prism shape. It will be understood that the mirror assembly130 could include more or less than three reflective surfaces.Accordingly, the mirror assembly 130 could be shaped as a multi-sidedprism shape having more or less than three reflective surfaces. Forexample, the mirror assembly 130 could have four reflective surfaces. Insuch scenarios, the mirror assembly 130 could have a square orrectangular cross-section.

lidar system 200 additionally includes an optical cavity 120 coupled tothe rotatable base 110. In such scenarios, the optical cavity 120includes a photodetector 122 and a photodetector lens 124 that arearranged so as to define a light-receiving axis. As such, an arrangementof the photodetector 122 and the photodetector lens 124 provide thelight-receiving axis. In some embodiments, the photodetector 122comprises a silicon photomultiplier (SiPM). However, other types ofphotodetectors, such as avalanche photodiodes (APDs) are contemplated.Furthermore, while photodetector 122 is described in the singular senseherein, it will be understood that systems incorporating multiplephotodetectors, such as a focal plane array, are also possible andcontemplated.

In example embodiments, the photodetector 122 could provide an outputsignal to the controller 150. For example, the output signal couldinclude information indicative of a time of flight of a given lightpulse toward a given portion of the field of view of the environment.Additionally or alternatively, the output signal could includeinformation indicative of at least a portion of a range map or pointcloud of the environment.

The lidar system 200 also includes a light-emitter device 126 and alight-emitter lens 128 that are arranged so as to define alight-emission axis. The light-emitter device 126 could include a laserdiode or another type of light-emitter. In some embodiments, thelight-emitter device 126 could be coupled to a laser pulser circuitoperable to cause the light-emitter device 126 to emit one or more laserlight pulses. In such scenarios, the laser pulser circuit could becoupled to a trigger source, which could include controller 150. Thelight-emitter device 126 could be configured to emit infrared laserlight (e.g., having a wavelength between 800-1600 nanometers). However,other wavelengths of light are possible and contemplated. Furthermore,it will be understood that sensing technologies utilizing non-pulsed(e.g., continuous wave) illumination are also contemplated. For example,frequency-modulated continuous wave (FM-CW) and continuous wavetime-of-flight (CW-TOF) systems are possible within the scope of thepresent disclosure.

In some embodiments, the light-emitter device 126 is configured to emitlight pulses (by way of light-emitter lens 128) that interact with themirror assembly 130 such that the light pulses are redirected toward anenvironment (e.g., an external environment of a vehicle). In suchscenarios, at least a portion of the light pulses are reflected backtoward the lidar system 200 and received by the photodetector 122 (byway of photodetector lens 124) so as to determine at least one of arange or a point cloud.

At least one light source (e.g., the light-emitter device 126) of thelidar system 200 could be configured to emit light pulses. The emittedlight pulses interact with the environment to provide return lightpulses. At least one detector (e.g., the photodetector 122) of the lidarsystem 200 could be configured to detect at least a portion of thereturn light pulses.

The lidar system 200 includes a controller 150. The controller 150includes at least one of a field-programmable gate array (FPGA) or anapplication-specific integrated circuit (ASIC). Additionally oralternatively, the controller 150 may include one or more processors 152and a memory 154. The one or more processors 152 may be ageneral-purpose processor or a special-purpose processor (e.g., digitalsignal processors, etc.). The one or more processors 152 may beconfigured to execute computer-readable program instructions that arestored in the memory 154. As such, the one or more processors 152 mayexecute the program instructions to provide at least some of thefunctionality and operations described herein.

The memory 154 may include, or take the form of, one or morecomputer-readable storage media that may be read or accessed by the oneor more processors 152. The one or more computer-readable storage mediacan include volatile and/or non-volatile storage components, such asoptical, magnetic, organic or other memory or disc storage, which may beintegrated in whole or in part with at least one of the one or moreprocessors 152. In some embodiments, the memory 154 may be implementedusing a single physical device (e.g., one optical, magnetic, organic orother memory or disc storage unit), while in other embodiments, thememory 154 can be implemented using two or more physical devices.

As noted, the memory 154 may include computer-readable programinstructions that relate to operations of lidar system 200. As such, thememory 154 may include program instructions to perform or facilitatesome or all of the functionalities described herein.

As an example, the operations could include causing the at least onelight source (e.g., light-emitter device 126) to emit one or more lightpulses.

The operations could additionally include receiving at least a firstportion of the return light pulses from the default field of view 102 asa first detected light signal.

The operations may further include receiving at least a second portionof the return light pulses from the extended field of view 182 as asecond detected light signal.

The operations yet further include determining, based on the firstdetected light signal and the second detected light signal, a pointcloud indicative of objects within the default field of view 102 and theextended field of view 182.

Additionally, the operations could include receiving a reflection map.As an example, the reflection map could include reflection informationabout how the reflective surface 180 reflects the light pulses into theextended field of view 182. In such scenarios, determining the pointcloud is further based on the reflection map.

As an example embodiment, the reflection information could include atleast one of: an angle of the reflective surface 180, a pose ororientation of the reflective surface 180, or a surface curvature of thereflective surface 180. Additionally or alternatively, the reflectioninformation could include a look up table (LUT). In such scenarios, theLUT could include information indicative of: a default light pulseemission vector and a reflected light pulse emission vector.

In various embodiments, the lidar system 200 includes a housing 160having a plurality of optical windows 162. The optical windows 162 couldbe substantially transparent to wavelengths of light such as the emittedlight pulses. For example, the optical windows 162 could includetransparent materials configured to transmit the emitted light pulseswith a transmission efficiency greater than 80%. In some embodiments,the housing 160 could include two elongate optical windows. The opticalwindows 162 could be arranged on substantially opposite surfaces of thehousing 160. In such scenarios, the light pulses could be emitted towardthe environment by optical transmission through the plurality of opticalwindows 162.

In some embodiments, the lidar system 200 could include a prismatic lens140 configured to refract the light pulses. The prismatic lens 140 couldinclude an optical element (e.g., a prism lens). In some embodiments,the prismatic lens 140 could cause the light emitted from the opticalcavity to be refracted at a different angle from the axis of the opticalcavity. In such a manner, the optical axis of the beam coming out of thecavity itself can be decoupled from the angle of the optical cavity.Utilizing one or more prismatic lenses 140 could provide a shifted fieldof view to be asymmetric without having to adjust the optical cavityangle by the same amount. Thus, the prismatic lens 140 could provide theflexibility of smaller package size. For example, in some embodiments,the optical cavity 120 could remain substantially vertical, but the beamemitted by the optical cavity 120 could be angled. Accordingly, opticalcavities 120 that utilize prismatic lenses could provide benefits of anasymmetric field of view without widening, or otherwise physicallyrearranging, the space occupied by the optical cavity 120. In exampleembodiments, the prismatic lens 140 could replace the light-emitter lens128. In other embodiments, the prismatic lens 140 could be utilized inaddition to the light-emitter lens 128.

In some embodiments, a prismatic lens 140 could be utilized in place ofthe photodetector lens 124 or in conjunction with the photodetector lens124. For example, the prismatic lens 140 could be used along thelight-receiving axis 125 so as to modify the field of view from whichlight pulses could be received.

Additionally or alternatively, the light pulses emitted or transmittedthrough the plurality of optical windows 162 could form an asymmetriclight emission pattern in the environment. For example, the light pulsesemitted through a first window of the plurality of windows are emittedwithin a first emission angle range, and wherein the light pulsesemitted through a second window of the plurality of windows are emittedwithin a second emission angle range, wherein the asymmetric lightemission pattern is provided by the first emission angle range beingdifferent from the second emission angle range.

In some embodiments, the extended field of view 182 and the defaultfield of view 102 are not fully overlapping. For example, the defaultfield of view 102 may include an angled annular region substantiallycentered about the first axis of lidar system 200. The default field ofview 102 could include an elevation angle range between 2 degrees abovethe horizon and 18 degrees below the horizon in the scenario where thefirst axis is arranged perpendicular to the horizon (e.g., vertically).It will be understood that other orientations, geometries, and shapes ofthe default field of view 102 are possible and contemplated.

The extended field of view 182 could include a region directed downwardand/or upward with respect to the first axis of the lidar system 200. Insome embodiments, the extended field of view 182 includes regions thatare not coextensive with the default field of view 102. In suchscenarios, the extended field of view 182 could provide a larger overallregion in which the lidar system 200 could detect objects. For example,the default field of view 102 could define at least one blind region. Insuch situations, the extended field of view 182 could overlap with atleast a portion of the at least one blind region.

Additionally or alternatively, the extended field of view 182 couldinclude regions that are coextensive with the default field of view. Insuch scenarios, the coextensive portions of the extended field of view182 and the default field of view 102 could provide higher rate and/orhigher resolution detection of objects by the lidar system 200.

In some embodiments, the reflective surface 180 could include at leastone of: a flat mirror, a convex mirror, a concave mirror, or amultifaceted mirror array. Other types of reflective materials and/orsurfaces are possible and contemplated. In some embodiments, thereflective surface 180 could include a flat mirror having a flatness ofbetween λ and λ/100 as measured with an optical interference technique,where the light pulses emitted by the light-emitter device 126 include awavelength, λ.

In various embodiments, the lidar system 200 could include at least onebaffle 170. In such scenarios, the at least one baffle 170 could beconfigured to reduce stray light within the optical cavity 120. In anexample embodiment, the baffle 170 could include an optically-opaquematerial disposed between the light-receiving axis and thelight-emission axis.

The lidar system 200 also includes at least one beam stop 174. The beamstop 174 may be optically opaque and could be configured to block lightbeams from being emitted toward the optical windows 162 and/or towardthe environment. In some embodiments, the beam stop 174 may be arrangedwithin the housing 160 substantially opposite the optical cavity 120.

When light emitted from the optical cavity 120 interacts with a cornerof the mirror assembly 130 (e.g., at an intersection between twodifferent reflective surfaces 132), the light is split into two parts,one emitted forward (e.g., toward a first optical window), and oneemitted backward (e.g., toward a second optical window). To avoidambiguous lidar signals due to the two emitted pulses, the beam stop 174may be arranged near the top of the field of view so as to block atleast one of the two beams from being emitted toward the environment.Furthermore, by adjusting the beam stop 174, the field of view at thetop of one side can be expanded or extended at the expense of the fieldof view near the top of the other side.

In such scenarios, by adjusting the top beam stop position, the field ofview can be distributed between the two sides at the bottom and top ofthe field of view respectively.

FIGS. 2A, 2B, 2C, and 2D illustrates various views and portions of lidarsystem 200. FIG. 2A illustrates an oblique view of lidar system 200,according to an example embodiment. As illustrated, lidar system 200could include a rotatable base 110. The rotatable base 110 could beconfigured to rotate about first axis 111. Furthermore, lidar system 200could include an optical cavity 120, which could include light-emitterdevice 126, light-emitter lens 128, photodetector 122, and photodetectorlens 124. Furthermore, in some embodiments, lidar system 200 couldinclude a mirror assembly 130. The mirror assembly 130 could include aplurality of reflective surfaces 132 a, 132 b, and 132 c and a shaft134. The mirror assembly 130 could be configured to rotate about secondaxis 135.

In some embodiments, the light-emitter device 126 and the light-emitterlens 128 could form a light-emission axis 129. Light pulses emitted bythe light-emitter device 126 could interact with reflective surface 132b at a transmission mirror region 137.

In some embodiments, the photodetector 122 and the photodetector lens124 could form a light-receiving axis 125. Light pulses emitted by thelight-emitter device 126 could be reflected or otherwise interact withthe environment and could be observed at the photodetector 122 by way ofa receiving mirror region 139.

As illustrated in FIG. 2, lidar system 200 could include a baffle 170.The baffle 170 could include an opening 172 within which the mirrorassembly 130 could be disposed. The opening 172 could be shaped so as toprovide freedom for the mirror assembly 130 to rotate about the secondaxis 135.

FIG. 2B illustrates a side view of the lidar system 200 along the −ydirection, according to an example embodiment. As well as other elementsdescribed above in reference to FIG. 2A, lidar system 200 couldadditionally include a housing 160 and a plurality of optical windows,such as optical window 162 a.

FIG. 2C illustrates a mirror assembly 130 of the lidar system 200,according to an example embodiment. For example, mirror assembly 130could include a plurality of reflective surfaces 132 a, 132 b, and 132c. The mirror assembly 130 could additionally include a shaft 134, whichcould be configured to rotate about second axis 135.

In some embodiments, the light-emitter device 126 could emit lightpulses toward the mirror assembly 130 along a light-emission axis 129. Areflective surface 132 b of the mirror assembly 130 could reflect suchlight pulses at a transmission mirror region 137 such that the lightpulses are transmitted toward an external environment.

In such examples, light from the environment (e.g., reflected lightpulses) could be reflected by the reflective surface 132 b of the mirrorassembly 130 at a receiving mirror region 139. In some embodiments, thereceived light could be directed along light-receiving axis 125 towardthe photodetector 122.

FIG. 2D illustrates a view of the lidar system 200 along the −xdirection, according to an example embodiment. The lidar system 200could include the optical cavity 120 as being disposed such thatlight-emission axis 129 and/or light-receiving axis 125 aresubstantially parallel with the first axis 111.

In some embodiments, such an arrangement of the optical cavity 120 withrespect to the first axis 111 could provide a substantially symmetricemission pattern in an external environment at least because lightpulses emitted by the light-emitter device 126 are equally likely to betransmitted through a first optical window 162 a to the right (+ydirection) or through the second optical window 162 b to the left (−ydirection) based on the rotational position of the mirror assembly 130.

FIG. 3 illustrates a system 300, according to an example embodiment. Insome embodiments, system 300 could be similar or identical to system100, as illustrated and described in reference to FIG. 1. System 300includes a lidar system 200, as illustrated and described in referenceto FIG. 2. System 300 also includes a reflective surface 180. Asillustrated in FIG. 3, the reflective surface 180 could include a planarsurface (e.g., a flat mirror). However, other types of surfacesconfigured to reflective light pulses emitted by the lidar system 200are possible and contemplated. In some embodiments, the reflectivesurface 180 could be disposed within two feet of the lidar system 200.However, the reflective surface 180 could be disposed nearer to orfarther from the lidar system 200. Furthermore, although FIG. 3illustrates the reflective surface 180 as being separate from the lidarsystem 200, it will be understood that in some embodiments, thereflective surface 180 could be incorporated into the lidar system 200.

In some embodiments, the lidar system 200 could be configured to emitlight pulses that do not interact with the reflective surface 180 so asto provide a default field of view 102. Furthermore, the lidar system200 could be configured to emit light pulses that interact with thereflective surface 180 so as to provide an extended field of view 182.As illustrated, in some embodiments, the extended field of view 182could include a region substantially below (e.g., along the −zdirection) relative to the lidar system 200 along the first axis 111.

In some embodiments, the reflective surface 180 may represent astructural support for the lidar system 200 on a vehicle, such as amount or bracket, or a portion thereof. The reflective surface 180 couldinclude another type of static feature that would not normally representan interesting object within the field of view. In such a scenario, theextended field of view 182 could provide extended coverage for the lidarsystem 200 while more efficiently utilizing light pulses that may haveotherwise been ignored. That is, light pulses that would have otherwisereflected back to the lidar system 200 from a static support structureor mount, can be diverted toward the extended field of view 182, whichmay include interesting objects or other types of features (e.g.,obstacles, etc.). As illustrated in FIG. 3, the extended field of view182 could effectively include an area directly under the lidar system200. In such scenarios, lidar system 200 could be configured to detectobjects in the extended field of view 182 so as to sense pedestrians, aground surface, and/or other types of features.

As illustrated in FIG. 3, the lidar system 200 could emit light pulsesthat interact with the reflective surface 180 so as to provide aplurality of reflected light pulse emission vectors 310, 312, and 314.The reflected light pulse emission vectors 310, 312, and 314 could format least a portion of the extended field of view 182. While threereflected light pulse emission vectors are illustrated, it will beunderstood that more reflected light pulse emission vectors are possibleand contemplated.

FIG. 4 illustrates a system 400, according to an example embodiment. Insome embodiments, system 400 could be similar or identical to system 100and system 300, as illustrated and described in reference to FIG. 1 andFIG. 3. System 400 includes a lidar system 200, as illustrated anddescribed in reference to FIG. 2. System 400 also includes a reflectivesurface 180. As illustrated in FIG. 4, the reflective surface 180 couldinclude a plurality of surfaces. For example, the plurality of surfacescould include a first reflective surface 402 and a second reflectivesurface 404. Other types of surfaces configured to reflective lightpulses emitted by the lidar system 200 are possible and contemplated.

In some embodiments, the lidar system 200 could be configured to emitlight pulses that do not interact with the reflective surface 180 so asto provide a default field of view 102. Furthermore, the lidar system200 could be configured to emit light pulses that interact with firstreflective surface 402 so as to provide an extended field of view 182 a.As illustrated, in some embodiments, the extended field of view 182 acould include a region substantially below (e.g., along the −zdirection) relative to the lidar system 200 along the first axis 111.

Additionally, the lidar system 200 could be configured to emit lightpulses that interact with second reflective surface 404 so as to providean extended field of view 182 b. As illustrated, in some embodiments,the extended field of view 182 b could include a region substantiallyabove (e.g., along the +z direction) relative to the lidar system 200along the first axis 111.

In some scenarios, the extended fields of view 182 a and 182 b couldprovide extended coverage for the lidar system 200 while moreefficiently utilizing light pulses that may have otherwise been ignored.That is, light pulses that would have otherwise reflected back to thelidar system 200 to indicate a static support structure or mount, can bediverted toward the extended fields of view 182 a or 182 b, which mayinclude information about obstacles, other vehicles, pedestrians, orother types of features. As illustrated in FIG. 4, the extended field ofview 182 a could effectively include an area directly under the lidarsystem 200 and the extended field of view 182 b could effectivelyinclude an area directly over the lidar system 200. In such scenarios,lidar system 200 could be configured to detect objects in the extendedfields of view 182 a and 182 b so as to sense pedestrians, a groundsurface, and/or other types of features.

As illustrated in FIG. 4, the lidar system 200 could emit light pulsesthat interact with the reflective surface 402 so as to provide aplurality of reflected light pulse emission vectors 410, 412, and 414.The reflected light pulse emission vectors 410, 412, and 414 could format least a portion of the extended field of view 182 a. Additionally,the lidar system 200 could emit light pulses that interact with thereflective surface 404 so as to provide a plurality of reflected lightpulse emission vectors 416 and 418. The reflected light pulse emissionvectors 416 and 418 could form at least a portion of the extended fieldof view 182 b.

III. Example Vehicles

FIGS. 5A, 5B, 5C, 5D, and 5E illustrate a vehicle 500, according to anexample embodiment. The vehicle 500 could be a semi- or fully-autonomousvehicle. While FIGS. 5A-5E illustrate vehicle 500 as being an automobile(e.g., a passenger van), it will be understood that vehicle 500 couldinclude another type of autonomous vehicle, robot, or drone that cannavigate within its environment using sensors and other informationabout its environment.

The vehicle 500 may include one or more sensor systems 502, 504, 506,508, and 510. In some embodiments, sensor systems 502, 504, 506, 508,and 510 could include lidar sensors having a plurality of light-emitterdevices arranged over a range of angles with respect to a given plane(e.g., the x-y plane).

One or more of the sensor systems 502, 504, 506, 508, and 510 may beconfigured to rotate about an axis (e.g., the z-axis) perpendicular tothe given plane so as to illuminate an environment around the vehicle500 with light pulses. Based on detecting various aspects of reflectedlight pulses (e.g., the elapsed time of flight, polarization, intensity,etc.), information about the environment may be determined.

In an example embodiment, sensor systems 502, 504, 506, 508, and 510 maybe configured to provide respective point cloud information that mayrelate to physical objects within the environment of the vehicle 500.While vehicle 500 and sensor systems 502, 504, 506, 508, and 510 areillustrated as including certain features, it will be understood thatother types of sensor systems are contemplated within the scope of thepresent disclosure.

An example embodiment may include a system having a plurality oflight-emitter devices. The system may include a transmit block of alidar device. For example, the system may be, or may be part of, a lidardevice of a vehicle (e.g., a car, a truck, a motorcycle, a golf cart, anaerial vehicle, a boat, etc.). Each light-emitter device of theplurality of light-emitter devices is configured to emit light pulsesalong a respective beam elevation angle. The respective beam elevationangles could be based on a reference angle or reference plane. As anexample, the reference plane may be based on an axis of motion of thevehicle 500. Other reference angles (e.g., an angle of azimuth,elevation, etc.) or reference planes (e.g., x, y, and z planes) arecontemplated and possible within the scope of the present disclosure.

While lidar systems with single light-emitter devices are described andillustrated herein, lidar systems with multiple light-emitter devices(e.g., a light-emitter device with multiple laser bars on a single laserdie) are also contemplated. For example, light pulses emitted by one ormore laser diodes may be controllably directed about an environment ofthe system. The angle of emission of the light pulses may be adjusted bya scanning device such as, for instance, a mechanical scanning mirrorand/or a rotational motor. For example, the scanning devices couldrotate in a reciprocating motion about a given axis and/or rotate abouta vertical axis. In another embodiment, the light-emitter device mayemit light pulses towards a spinning prism mirror, which may cause thelight pulses to be emitted into the environment based on an angle of theprism mirror angle when interacting with each light pulse. Additionallyor alternatively, scanning optics and/or other types ofelectro-opto-mechanical devices are possible to scan the light pulsesabout the environment.

In some embodiments, a single light-emitter device may emit light pulsesaccording to a variable shot schedule and/or with variable power pershot, as described herein. That is, emission power and/or timing of eachlaser pulse or shot may be based on a respective elevation angle of theshot. Furthermore, the variable shot schedule could be based onproviding a desired vertical spacing at a given distance from the lidarsystem or from a surface (e.g., a front bumper) of a given vehiclesupporting the lidar system. As an example, when the light pulses fromthe light-emitter device are directed downwards, the power-per-shotcould be decreased due to a shorter anticipated maximum distance totarget. Conversely, light pulses emitted by the light-emitter device atan elevation angle above a reference plane may have a relatively higherpower-per-shot so as to provide sufficient signal-to-noise to adequatelydetect pulses that travel longer distances.

In some embodiments, the power/energy-per-shot could be controlled foreach shot in a dynamic fashion. In other embodiments, thepower/energy-per-shot could be controlled for successive set of severalpulses (e.g., 10 light pulses). That is, the characteristics of thelight pulse train could be changed on a per-pulse basis and/or aper-several-pulse basis.

While FIGS. 5A-5E illustrates various lidar sensors attached to thevehicle 500, it will be understood that the vehicle 500 couldincorporate other types of sensors, such as a plurality of opticalsystems (e.g., cameras), radars, or ultrasonic sensors.

In an example embodiment, vehicle 500 could include a lidar system(e.g., lidar system 200) configured to emit light pulses into anenvironment of the vehicle 500 so as to provide information indicativeof objects within a default field of view.

Yet further, the vehicle 500 includes a reflective surface (e.g.,reflective surfaces 180 a and 180 b) that is optically coupled to thelidar system. In such scenarios, the reflective surface is configured toreflect at least a portion of the emitted light pulses so as to providean extended field of view. The lidar system is further configured toprovide information indicative of objects within the extended field ofview.

In some embodiments, the reflective surface could include a portion of abody of the vehicle 500. For example, as illustrated in FIGS. 5A, 5B,and 5E, reflective surfaces 180 a and 180 b could located adjacent to agiven lidar system (e.g., sensor systems 508 and 510, respectively).

In some embodiments, the reflective surface could include at least oneof a rear view mirror of the vehicle or a side view mirror of thevehicle. Other reflective surfaces, including other body surfaces of thevehicle, are possible and contemplated.

As described in reference to FIG. 2, vehicle 500 could include one ormore lidar systems (e.g., lidar system 200), each of which may includeat least one light source configured to emit the light pulses. Theemitted light pulses interact with the environment to provide returnlight pulses.

The lidar system includes at least one detector configured to detect atleast a portion of the return light pulses. The lidar system alsoinclude a controller (e.g., controller 150) having at least oneprocessor (e.g., processor 152) and at least one memory (e.g., memory154). The at least one processor executes instructions stored in the atleast one memory so as to carry out operations. In some embodiments, theoperations include causing the at least one light source to emit thelight pulses. The operations could additionally include receiving atleast a first portion of the return light pulses from the default fieldof view as a first detected light signal. The operations could furtherinclude receiving at least a second portion of the return light pulsesfrom the extended field of view as a second detected light signal. Theoperations yet further include determining, based on the first detectedlight signal and the second detected light signal, a point cloudindicative of objects within the default field of view and the extendedfield of view.

The operations additionally include receiving a reflection map. Thereflection map could include reflection information about how thereflective surface reflects the light pulses into the extended field ofview. In such scenarios, determining the point cloud could be furtherbased on the reflection map. The reflection information could include atleast one of: an angle of the reflective surface, a pose of thereflective surface, or information regarding surface curvature of thereflective surface.

In embodiments that include a controller, the operations could includedetermining, based on the return light pulses, one or more stairobjects. The one or more stair objects could include individual steps ofa staircase or other similar objects. It will be understood that otherobjects and/or obstacles (e.g., doors, hallways, pathways, gates,windows, thresholds, etc.) are contemplated within the scope of thepresent disclosure.

In such scenarios, in response to determining the one or more stairobjects, the operations could include adjusting an operating behavior ofthe vehicle. For example, the operating behavior could be modified froma flat surface movement to a stair traversal movement. Other adjustmentsin operating behavior are possible and contemplated.

As described herein, the reflective surface could be disposed within twofeet of the lidar system. Alternatively, the reflective surface could bedisposed closer to, or farther from, the lidar system.

In some embodiments, at least a portion of the extended field of viewcould be disposed above the lidar system. Additionally or alternatively,at least a portion of the extended field of view could be disposed belowthe lidar system.

FIG. 6 illustrates a top view of an operating scenario 600, according toan example embodiment. The operating scenario 600 could include a lidarsystem 200 mounted along a right side of vehicle 500, along afront-right quarter panel. In an example embodiment, the lidar system200 could rotate about a first axis (e.g., first axis 111 and/or thez-axis). While it is rotating about the first axis, lidar system 200could emit light pulses into its environment by redirecting the lightpulses with the rotating mirror assembly (e.g., mirror assembly 130). Insuch a scenario, at least some of the light pulses may interact withreflective surface 180 so as to reflect some light pulses toward theextended field of view 182.

FIG. 6 illustrates an example light emission pattern along a groundsurface. As illustrated in FIG. 3, the light emission pattern along theground could include a portion of a default field of view 102 and aportion of the extended field of view 182. While FIG. 6 illustrates thedefault field of view 102 and the extended field of view 182 as beingnon-overlapping, in some embodiments, at least a portion of the defaultfield of view 102 could overlap with the extended field of view 182.

As illustrated in FIG. 6, the extended field of view 182 could providedetection of objects at close range to the vehicle 500 immediately belowthe lidar system 200. As such, the extended field of view 182 could bebeneficial because it could provide lidar coverage in conventionallyuncovered fields of view. Accordingly, the operating scenario 600 couldillustrate a system with better safety than that of conventionalsystems.

IV. Example Methods

FIG. 7 illustrates a method 700, according to an example embodiment. Itwill be understood that the method 700 may include fewer or more stepsor blocks than those expressly illustrated or otherwise disclosedherein. Furthermore, respective steps or blocks of method 700 may beperformed in any order and each step or block may be performed one ormore times. In some embodiments, some or all of the blocks or steps ofmethod 700 may be carried out by controller 150 and/or other elements ofsystems 100, 300, 400 and lidar system 200 as illustrated and describedin relation to FIG. 1, FIG. 3, FIG. 4, and FIG. 2A-2D, respectively.

Block 702 includes causing at least one light source (e.g.,light-emitter device 126) of a lidar system (e.g., lidar system 200) toemit light pulses toward a default field of view (e.g., default field ofview 102) and toward a reflective surface (e.g., reflective surface180). The reflective surface could be configured to reflect a portion ofthe light pulses toward an extended field of view (e.g., extended fieldof view 182). The emitted light pulses interact with an environment ofthe lidar system to provide return light pulses.

Block 704 includes receiving at least a first portion of the returnlight pulses from the default field of view as a first detected lightsignal. In some embodiments, receiving the first portion of the returnlight pulses could include detecting reflected light pulses from thedefault field of view. The first detected light signal could be formedbased on respective detections of the reflected light pulses by way ofone or more detectors (e.g., photodetector 122).

Block 706 includes receiving at least a second portion of the returnlight pulses from the extended field of view as a second detected lightsignal. In some embodiments, receiving the second portion of the returnlight pulses could include detecting reflected light pulses from theextended field of view. The second detected light signal could be formedbased on respective detections of the reflected light pulses by way ofone or more detectors (e.g., photodetector 122).

Block 708 includes determining, based on the first detected light signaland the second detected light signal, a point cloud indicative ofobjects within the default field of view and the extended field of view.In some embodiments, determining the point cloud could includeassociating the first detected light signal and the second detectedlight signal with a plurality of spatial range points. For example, eachspatial range point could be determined based on an emission angle and atime of flight between an initial firing time and a subsequent detectiontime for each respective light pulse.

In some embodiments, the extended field of view and the default field ofview are not fully overlapping. For example, the default field of viewcould define at least one blind region. In such scenarios, the extendedfield of view could overlap with at least a portion of the at least oneblind region.

In some embodiments, method 700 could additionally include receiving areflection map. In examples, the reflection map could be received by thecontroller 150 by way of a wired or wireless communication interface. Insome embodiments, the reflection map could be provided based on acalibration target and/or a calibration procedure. The reflection mapcould be stored in memory 154 or another local memory.

In some embodiments, the reflection map includes reflection informationabout how the reflective surface reflects the light pulses into theextended field of view. As an example, the reflection map could includea correspondence between an emission angle in elevation and azimuth anda reflected light pulse emission vector that intersects the extendedfield of view. In such scenarios, determining the point cloud could befurther based on the reflection map.

In some examples, the reflection information could include at least oneof: an angle of the reflective surface, a pose of the reflectivesurface, or a surface curvature of the reflective surface.

Additionally or alternatively, the reflection information could includea look up table (LUT). As an example, the LUT could include informationindicative of: a default light pulse emission vector and a reflectedlight pulse emission vector.

The arrangements shown in the Figures should not be viewed as limiting.It should be understood that other embodiments may include more or lessof each element shown in a given Figure. Further, some of theillustrated elements may be combined or omitted. Yet further, anillustrative embodiment may include elements that are not illustrated inthe Figures.

A step or block that represents a processing of information cancorrespond to circuitry that can be configured to perform the specificlogical functions of a herein-described method or technique.Alternatively or additionally, a step or block that represents aprocessing of information can correspond to a module, a segment, or aportion of program code (including related data). The program code caninclude one or more instructions executable by a processor forimplementing specific logical functions or actions in the method ortechnique. The program code and/or related data can be stored on anytype of computer readable medium such as a storage device including adisk, hard drive, or other storage medium.

The computer readable medium can also include non-transitory computerreadable media such as computer-readable media that store data for shortperiods of time like register memory, processor cache, and random accessmemory (RAM). The computer readable media can also includenon-transitory computer readable media that store program code and/ordata for longer periods of time. Thus, the computer readable media mayinclude secondary or persistent long term storage, like read only memory(ROM), optical or magnetic disks, compact-disc read only memory(CD-ROM), for example. The computer readable media can also be any othervolatile or non-volatile storage systems. A computer readable medium canbe considered a computer readable storage medium, for example, or atangible storage device.

While various examples and embodiments have been disclosed, otherexamples and embodiments will be apparent to those skilled in the art.The various disclosed examples and embodiments are for purposes ofillustration and are not intended to be limiting, with the true scopebeing indicated by the following claims.

What is claimed is:
 1. A system comprising: a lidar system configured toemit light pulses into an environment of the system so as to provideinformation indicative of objects within a default field of view,wherein the lidar system comprises: a rotatable base configured torotate about a first axis; a rotatable mirror coupled to the rotatablebase, wherein the rotatable mirror is configured to rotate about asecond axis; at least one light source configured to emit the lightpulses, wherein the emitted light pulses interact with the environmentto provide return light pulses; and at least one detector configured todetect at least a portion of the return light pulses; and a reflectivesurface optically coupled to the lidar system, wherein the reflectivesurface is configured to reflect at least a portion of the emitted lightpulses so as to provide an extended field of view, wherein the lidarsystem is further configured to provide information indicative ofobjects within the extended field of view.
 2. The system of claim 1,wherein the extended field of view and the default field of view are notfully overlapping.
 3. The system of claim 1, wherein the default fieldof view defines at least one blind region, and wherein the extendedfield of view overlaps with at least a portion of the at least one blindregion.
 4. The system of claim 1, wherein the reflective surfacecomprises at least one of: a flat mirror, a convex mirror, a concavemirror, or a multifaceted mirror array.
 5. The system of claim 1,wherein the light pulses comprise light having a wavelength of λ,wherein the reflective surface comprises a flat mirror having a flatnessof between λ and λ/100 as measured with an optical interferencetechnique.
 6. The system of claim 1, wherein the reflective surface isdisposed within two feet of the lidar system.
 7. The system of claim 1,further comprising: a controller comprising at least one processor andat least one memory, wherein the at least one processor executesinstructions stored in the at least one memory so as to carry outoperations, the operations comprising: causing the at least one lightsource to emit the light pulses; receiving at least a first portion ofthe return light pulses from the default field of view as a firstdetected light signal; receiving at least a second portion of the returnlight pulses from the extended field of view as a second detected lightsignal; and determining, based on the first detected light signal andthe second detected light signal, a point cloud indicative of objectswithin the default field of view and the extended field of view.
 8. Thesystem of claim 7, wherein the operations further comprise: receiving areflection map, wherein the reflection map comprises reflectioninformation about how the reflective surface reflects the light pulsesinto the extended field of view, wherein determining the point cloud isfurther based on the reflection map.
 9. The system of claim 8, whereinthe reflection information comprises at least one of: an angle of thereflective surface, a pose of the reflective surface, or a surfacecurvature of the reflective surface.
 10. A method comprising causing atleast one light source of a lidar system to emit light pulses toward adefault field of view and toward a reflective surface configured toreflect a portion of the light pulses toward an extended field of view,wherein the emitted light pulses interact with an environment of thelidar system to provide return light pulses, wherein the lidar systemcomprises: a rotatable base configured to rotate about a first axis; arotatable mirror coupled to the rotatable base, wherein the rotatablemirror is configured to rotate about a second axis; at least one lightsource configured to emit the light pulses, wherein the emitted lightpulses interact with the environment to provide return light pulses; andat least one detector configured to detect at least a portion of thereturn light pulses; receiving at least a first portion of the returnlight pulses from the default field of view as a first detected lightsignal; receiving at least a second portion of the return light pulsesfrom the extended field of view as a second detected light signal; andtransmitting point cloud data, wherein the point cloud data is based onthe first detected light signal and the second detected light signal,and indicative of objects within the default field of view and theextended field of view.
 11. The method of claim 10, wherein the extendedfield of view and the default field of view are not fully overlapping.12. The method of claim 10, wherein the default field of view defines atleast one blind region, and wherein the extended field of view overlapswith at least a portion of the at least one blind region.
 13. The methodof claim 10, further comprising: receiving a reflection map, wherein thereflection map comprises reflection information about how the reflectivesurface reflects the light pulses into the extended field of view,wherein determining the point cloud is further based on the reflectionmap.
 14. The method of claim 13, wherein the reflection informationcomprises at least one of: an angle of the reflective surface, a pose ofthe reflective surface, or a surface curvature of the reflectivesurface.
 15. A vehicle comprising: a lidar system configured to emitlight pulses into an environment of the vehicle so as to provideinformation indicative of objects within a default field of view,wherein the lidar system comprises: a rotatable base configured torotate about a first axis; a rotatable mirror coupled to the rotatablebase, wherein the rotatable mirror is configured to rotate about asecond axis; at least one light source configured to emit the lightpulses, wherein the emitted light pulses interact with the environmentto provide return light pulses; and at least one detector configured todetect at least a portion of the return light pulses; and a reflectivesurface optically coupled to the lidar system, wherein the reflectivesurface is configured to reflect at least a portion of the emitted lightpulses so as to provide an extended field of view, wherein the lidarsystem is further configured to provide information indicative ofobjects within the extended field of view.
 16. The vehicle of claim 15,wherein the reflective surface comprises a portion of a body of thevehicle.
 17. The vehicle of claim 15, wherein the reflective surfacecomprises at least one of a rear view mirror of the vehicle or a sideview mirror of the vehicle.
 18. The vehicle of claim 15, wherein thelidar system comprises: a controller comprising at least one processorand at least one memory, wherein the at least one processor executesinstructions stored in the at least one memory so as to carry outoperations, the operations comprising: causing the at least one lightsource to emit the light pulses; receiving at least a first portion ofthe return light pulses from the default field of view as a firstdetected light signal; receiving at least a second portion of the returnlight pulses from the extended field of view as a second detected lightsignal; transmitting point cloud data, wherein the point cloud data isbased on the first detected light signal and the second detected lightsignal, and indicative of objects within the default field of view andthe extended field of view; and receiving a reflection map, wherein thereflection map comprises reflection information about how the reflectivesurface reflects the light pulses into the extended field of view,wherein the point cloud data is further based on the reflection map,wherein the reflection information comprises at least one of: an angleof the reflective surface, a pose of the reflective surface, or asurface curvature of the reflective surface.
 19. The vehicle of claim 15further comprising: a controller comprising at least one processor andat least one memory, wherein the at least one processor executesinstructions stored in the at least one memory so as to carry outoperations, the operations comprising: causing the at least one lightsource to emit the light pulses; receiving at least a first portion ofthe return light pulses from the default field of view as a firstdetected light signal; receiving at least a second portion of the returnlight pulses from the extended field of view as a second detected lightsignal; determining, based on the return light pulses, one or more stairobjects; and in response to determining the one or more stair objects,adjusting an operating behavior of the vehicle.
 20. The vehicle of claim15, wherein the reflective surface is disposed within two feet of thelidar system.
 21. The vehicle of claim 15, wherein at least a portion ofthe extended field of view is disposed above the lidar system.
 22. Thevehicle of claim 15, wherein at least a portion of the extended field ofview is disposed below the lidar system.